Disclosed are an anionic drug-containing polymeric micelle particle comprising: an anionic drug as an active ingredient; a cationic lipid; and an amphiphilic block copolymer, wherein the anionic drug forms a complex with the cationic lipid, and the complex is entrapped in the micelle structure of the amphiphilic block copolymer, and a method for preparing the same. The particle may increase stability of the anionic drug in blood or in a body fluid, and it may enable intracellular delivery to improve efficacy of anionic drugs.